When drilling earthen formations in pursuit of hydrocarbons or other resources, drilling fluid, also known as “mud,” is pumped into the wellbore. The drilling fluid lubricates the drill bit, transports borehole cuttings to the surface, and maintains wellbore pressure. If the pressure of the fluids in the formations being drilled accidentally or intentionally exceeds the pressure of the drilling fluid in the wellbore, an under balance situation arises, and fluid flows from the formations into the wellbore. Under such conditions, especially if a high pressure gas zone is drilled, the gas flows from the formations into the wellbore and travels toward the surface to produce what is known as a “kick.” A kick is a safety concern in drilling operations as the gas can interfere with mud flow and upon reaching the surface can inadvertently be set aflame or caused to explode.
If a kick can be detected and the rig operator notified before the kick reaches the surfaces, the operator can take actions reduce and/or eliminate adverse effects of the kick. Accordingly, techniques for timely detection of a kick are desirable.